The present invention relates to a vibration isolating mount having a toe correcting mechanism used in suspension or the like of a vehicle.
Conventionally, a vibration isolating mount having a toe correcting mechanism of this kind has been used in, for example, a rear suspension of an automobile. FIG. 8 is a plane view showing a rear suspension of an automobile in which both left and right side of suspension arms 100 are connected to a torsion beam 101, wheels 104 are attached to outer end sides of wheel shafts 103 and vibration isolating mounts 105, attached to connection cylinders at front ends of the arms 100, are connected to vehicle side brackets 106 by bolts and nuts.
FIG. 9 shows a sectional view of the conventional vibration isolating mount 105. The left or right vibration isolating mount 105 is provided with a shaft member, such as an inner cylinder 108, through a center hole 108a of which a bolt is penetrated, an outer cylinder 109, a rubber-like elastic body 110 interposed between the inner cylinder 108 and the outer cylinder 109, and a toe correcting mechanism 111 formed at one end portion of the vibration isolating mount 105.
According to the toe correcting mechanism 111, an inclined plate 112 is welded to one outer side of one end portion of the inner cylinder 108, a taper portion 113 is formed to expand at an end portion of the outer cylinder 109 opposite to the inclined plate 112 and a rubber-like elastic body 110a is interposed between the taper portion 113 and the inclined plate 112, by which thrust force which is force in the axial direction (length direction of inner cylinder) inputted from the suspension arm 100 by cornering force or the like, is dispersed in the direction orthogonal to the axial direction and operates a moment for leading the suspension arm 100 to the toe-in side.
In order to achieve compliance steering by the toe correcting mechanism 111 a spring constant of the rubber-like elastic body 110 must be restrained low, however, by setting the low spring constant, displacement of the rubber-like elastic body 110 in the axial direction is increased and durability of rubber is deteriorated. Therefore, in order to promote the durability of rubber by restraining the displacement of the rubber-like elastic body 110, the vibration isolating mount 105 is installed with a stopper 115 for restraining the displacement of the outer cylinder 109 in the axial direction to a predetermined amount against input of thrust in the axial direction.
The stopper 115 is constituted by a stopper metal piece 117 in a plate-like shape which is welded to an end portion of the inner cylinder 108, a reinforcement metal piece 118 which is welded to the inner cylinder 108 in parallel therewith. A stopper rubber 119 covers the stopper metal piece 117 and the reinforcement metal piece 118. A predetermined amount of a gap 122 is maintained between the stopper rubber 119 and an end flange 121 of the outer cylinder 109.
Further, there is adopted a constitution in the rubber-like elastic body 110 in which bored portions 120 at least one end of each of which are opened and which are holes or gaps extending in the axial direction are formed at a plurality of locations of the surrounding of the inner cylinder 108, by which spring constant in a direction orthogonal to the axial direction is lowered and ride quality is promoted.
Such a conventional vibration isolating mount 105 has difficulties such as the cost is high, a structure of a rubber vulcanizing mold is complicated and product weight is heavy. That is, according to the conventional vibration isolating mount 105, in order to promote durability of the rubber-like elastic body 110 having the low spring constant for achieving compliance characteristic, the stopper 115 is installed at end portion of the inner cylinder 108 with a gap 122 between the stopper 115 and the end portion 121 of the outer cylinder 109 and, the bored portions 120 are formed in the rubber-like elastic body 110 in the axial direction to lower the spring constant of the vehicle in the forward and rearward direction (direction orthogonal to axial direction) and to promote ride quality.
A direction of opening the gap 122 and a direction of opening the bored portion 120 are different from each other. Thus, a core die for forming the bored portions and a core die for forming the gap of the stopper are needed in the rubber vulcanizing mold in fabricating the vibration isolating mount since directions of drawing the core dies after molding are different from each other. Accordingly, there are difficulties in which fabrication of a product is complicated and the cost is high.
Furthermore, when the bored portion 120 are formed deeply to make the spring constant in the axial direction as uniform as possible, a thin film 123 is formed between a bottom portion 120a of the bored portion 120 and the gap 122 of the stopper 115. According to the thin film structure, when load resulting in large displacement is applied, the thin film 123 is often broken a constitutes a start point of crack, rupture and crack is propagated to a main body side of the rubber-like elastic body 110 to thereby cause deterioration in the durability of the vibration isolating mount 105.
Further, strength is needed in the stopper metal piece 117 against input of large load in the left and right direction (axial direction) of the vehicle. The reinforcement metal piece 118 needs to be installed separately from the stopper metal piece 117 or a plate thickness of the stopper metal piece 117 needs to increase, thereby causing a difficulty in which the weight of the vibration isolating mount is increased. Further, the stopper metal piece 117 and the reinforcement metal piece 118 must be welded to the outer peripheral face of the inner cylinder 108 and accordingly, the fabrication cost is increased.
Hence, it is a first object of the present invention to provide a vibration isolating mount achieving light-weighted formation by abolishing a stopper metal piece and a reinforcement metal piece on a side of an inner cylinder by changing a shape of an outer cylinder, achieving reduction in fabrication cost by simplifying structure of a mold die in vulcanizing rubber and which is excellent in durability.
In the meantime, according to the vibration isolating mount having the toe correcting mechanism mentioned above, in order to apply preliminary compression on the rubber-like elastic body 110 interposed between the inner cylinder 108 and the outer cylinder 109, as shown by FIG. 10, diameter reducing process is carried out on the outer cylinder 109. In that case, the preliminary compression is difficult to apply, to the rubber-like elastic body 110a interposed between the inclined plate 112 and the taper portion 113 which are opposed to each other, since the inner cylinder 108 is moved in a direction designated by an arrow mark P by reaction force of rubber when the outer cylinder 109 is compressed in the radius direction. Tensile force is exerted on an outer peripheral portion 110b of the rubber-like elastic body 110 by moving the inner cylinder 108 and distortion caused by the tensile force deteriorates durability of the rubber-like elastic body 110. Meanwhile, according to such a conventional vibration isolating mount, as shown by FIG. 10, a restraining member 125 for restraining displacement of the inner cylinder 108 in a direction orthogonal to the axial direction may be attached press-fit to the inner cylinder 108.
Hence, it is a second object of the present invention to alleviate distortion of a rubber-like elastic body at diameter reducing process by utilizing a restraining member for restraining displacement of an inner cylinder and finding a novel constitution at its surrounding portion to thereby fabricate a vibration isolating mount having the restraining member at a low cost.
According to a first embodiment of the present invention resolving the above-described first problem, there is provided a vibration isolating mount comprising a shaft member, an outer cylinder arranged at a surrounding of the shaft member and a rubber-like elastic body interposed between the shaft member and the outer cylinder, and having a toe correcting mechanism comprising an inclined face fixed at an outer side portion of an end portion of the shaft member, a taper portion formed at an end portion of the outer cylinder opposed to the inclined face and toe correcting rubber portion interposed between the taper portion and the inclined face, and having a stopper for restraining a displacement of the rubber-like elastic body in an axial direction, wherein a portion of the outer cylinder on a side opposed to the toe correcting mechanism interposing the shaft member is extended in the axial direction of the shaft member to form an extended portion and a stopper rubber portion of the stopper is arranged at a front end of the extended portion.
According to the above-described embodiment, in displacing the outer cylinder in the axial direction, the stopper rubber portion arranged at the front end of the extended portion is brought into press contact with a vehicle side bracket by which the displacement of the outer cylinder in the axial direction is further restrained.
In this way, by adopting an embodiment in which a portion of the outer cylinder on a side opposed to the toe correcting mechanism interposing the shaft member is extended in the axial direction and the stopper rubber is arranged at the front end of the extended portion to provide the side of the outer cylinder with stopper function restraining the displacement of the outer cylinder in the axial direction in a predetermined amount, the gap between the stopper and the outer cylinder in the conventional case is dispensed with and a core mold for forming the gap is dispensed with. Therefore, even when bored portions are provided in the rubber-like elastic body, the vibration isolating mount can be fabricated only by attaching a core mold for forming the bored portions at either die of a metal mold of a type divided into upper and lower dies and dividing the metal mold into the upper and lower dies after vulcanizing and molding rubber. Further, a thin film is not constituted between the bored portion and the gap of the stopper as in the conventional case and durability of the rubber-like elastic body is also promoted. Further, the stopper metal piece and the reinforcement metal piece can be abolished and light-weight formation of the vibration isolating mount can be achieved. Further, this is a measure only extending a portion of the outer cylinder and accordingly, a number of parts is small and reduction in the fabrication cost is feasible.
According to the vibration isolating mount having the above-described embodiment, it is preferable that both ends of the outer cylinder are arranged to a vehicle side bracket fixedly connected with both ends of the shaft member with gaps in the axial direction and a distance between an end of the outer cylinder on the side of the stopper and the vehicle side bracket opposed thereto is set to be equal to or shorter than a distance between an end of the outer cylinder on a side opposed to the stopper and the vehicle side bracket opposed thereto.
Such vibration isolating mounts are normally arranged in a pair symmetrically in the left and right direction when they are arranged in a vehicle and accordingly, when the outer cylinder is displaced in the axial direction toward the side of the stopper in one of the vibration isolating mounts, at the other of the vibration isolating mounts, the outer cylinder is displaced in the axial direction toward a side opposed to the stopper. Accordingly, by making the distance from the end of the outer cylinder on the side of the stopper to the vehicle side bracket equal to or shorter than the distance from the end of the outer cylinder on the side opposed to the stopper to the vehicle side bracket as mentioned above, when the stopper rubber is compressed by the vehicle side bracket by operating the stopper by the displacement in the axial direction in one of the vibration isolating mounts, at the other of the vibration isolating mounts, the end of the outer cylinder on the side opposed to the stopper can be prevented from being brought into contact with the vehicle side bracket. That is, interference between the end of the outer cylinder on the side opposed to the stopper where rubber is not arranged and the vehicle side bracket is prevented.
Further, by constituting such a dimensional setting, promotion of durability of the rubber-like elastic body can be achieved by prolonging the length of the outer cylinder in the axial direction as long as possible while guaranteeing that the above-described interference is not caused.
According to the above-described constitution, it is preferable to form a flange for the stopper extending in a direction orthogonal to the axial direction at a front end of an extended portion of the outer cylinder and fixing stopper rubber at an outer face thereof. Thereby, the stopper rubber can be fixedly adhered over a wide range and the displacement of the outer cylinder in the axial direction can be dealt with. As an embodiment, a flange for a stopper which is formed in a shape of a fan centering on the axis center of the shaft member so that the stopper rubber can be fixedly adhered over a wide range.
Further, as a measure for achieving further light-weight formation of the vibration isolating mount, in place of the inclined plate welded to the shaft member, an embodiment in which a projected portion made of resin having an inclined face is integrally molded to the shaft member can be adopted. In this case, resin is adopted as the material of the projected portion and accordingly, an amount of toe correction can simply be adjusted by changing a shape thereof.
Various materials can be adopted for resin constituting the projected portion and engineering plastic excellent in abrasion resistance, heat resistance and mechanical strength such as nylon, polycarbonate (PC), polyphenylene oxide (PPO), polyoxyethylene (acetal resin POM), polybutyleneterephthalate (PBT) and the like can be adopted. Further, for the projected portion made of resin, special engineering plastic achieving function superior to general engineering plastic such as polyethersulfone (PES), polyetherketone (PEEK), polyphenylene sulfide(PPS), polyimide (PI) and the like can be adopted.
As a shape of the projected portion, any shape can be adopted so far as it has an inclined face opposed to the taper portion of the side of the outer cylinder and does not effect influence on the stopper function of the stopper disposed on the opposed side interposing the shaft member, for example, a projected portion projected from the shaft member in a shape of a lump and having a fan-like shape in view from the axial direction can be adopted. Although a spread angle of the fan shape can pertinently be selected in accordance with the toe correction function, a range of 60xc2x0 through 150xc2x0 is preferable and a range of 100xc2x0 through 120xc2x0 is more preferable.
Further, it is preferable that the projected portion is formed with a wide width in the axial direction such that it can withstand large load from the axial direction. Specifically, a structure having a shape of a right-angled triangle in respect of a longitudinal sectional shape cut in the axial direction can be exemplified. Although any fixing means can be adopted so far as it can solidly fix the projected portion to the shaft member, when an embodiment in which a fixing portion having a cylindrical shape with a wide width in the axial direction which is integrally formed to the projected portion is fittedly fixed to the shaft member is adopted, even when a large load is applied from the axial direction, sufficient strength can be maintained. Either of adherence, press-fitting and fixing by shrinking of resin at molding can be adopted for fixing the projected portion with the shaft member, and a fixing surface of the shaft member can be uneven.
The inclined face of the projected portion is an inclined face inclined to the axial direction of the shaft member. That is, the inclined face is inclined such that a height of projection of the projected portion is gradually lowered from one side to other side of the shaft member in the axial direction. Further, the taper portion on the side of the outer cylinder opposed to the inclined face is embodied having an inclined face in parallel therewith. An angle of inclination of the inclined face can pertinently be selected in accordance with toe correction function and an angle of 30xc2x0 through 60xc2x0 is preferable. Further, the projected portion is made of resin and is integrally molded with the shaft member and accordingly, the step of welding the inclined plate as in the above-described conventional case can be omitted and reduction of fabrication cost is made feasible.
In respect of a relationship between the stopper rubber and the rubber-like elastic body, either of a continuous structure and a separated structure of the stopper rubber and the rubber-like elastic body can be adopted so far as it is an embodiment in which the stopper rubber is arranged at a front end of the extended portion of the outer cylinder and is applicable regardless of presence or absence of the bored portion in the axial direction of the rubber-like elastic body.
In this case, the bored portion is referred to as a hole or an air gap extending in the axial direction, at least one end of which is opened, and in the vibration isolating mount formed with the bored portion, an embodiment in which the bored portion penetrates the rubber-like elastic body in the axial direction can be adopted and accordingly, the spring constant in a direction orthogonal to the axial direction can be designed uniformly in the axial direction. Further, when a structure in which the bored portion penetrates the rubber-like elastic body is adopted, different from the conventional structure in which the thin film is formed between the bottom portion of the bored portion and the gap of the stopper, breakage of the thin film by large load is totally dispensed with and durability of rubber is promoted which is preferable.
Further, the shaft member is not restricted to a cylindrical member such as an inner cylinder but may be a member in a solid state. Further, in respect of the taper portion and the extended portion in the outer cylinder, the outer cylinder member made of a metal can be integrally formed simply by pressing or the like. According to the vibration isolating mount, the projected portion is integrally fixed to the end portion of the shaft member, nonvulcanized rubber-like elastic body is respectively interposed between the shaft member and the outer cylinder and fixed to the toe correction portion and the stopper portion and thereafter, molded by integrally adhering rubber by vulcanizing it in a metal mold and thereafter, durability of the rubber-like elastic body may be promoted by reducing the diameter of the cylindrical portion of the outer cylinder.
According to a second embodiment of the present invention resolving the above-described second problem, there is provided a vibration isolating mount comprising a shaft member, an outer cylinder arranged at a surrounding of the shaft member and a rubber-like elastic body interposed between the shaft member and the outer cylinder, further having a toe correcting mechanism comprising a projected portion integrated to an outer side portion of the shaft member and having an inclined face inclined to an axial direction of the shaft member, a taper portion formed at a portion of the outer cylinder opposite to the inclined face, and a toe correcting rubber portion interposed between the taper portion and the inclined face and continuous to the rubber-like elastic body, wherein a restraining member projected from the shaft member to an outer side for restraining a displacement of the shaft member in a direction orthogonal to the axial direction is integrally formed with the projected portion remotely from the inclined face of the projected portion in the axial direction by a predetermined distance, by a synthetic resin and via a cylindrical portion externally fitted onto the shaft member and the rubber-like elastic body is interposed between the restraining member and the projected portion.
In such an embodiment, when diameter reducing process is carried out on the outer cylinder, force applied on the rubber-like elastic body is received by the inclined face of the projected portion of the shaft member and a face of the restraining member on the side of the projected portion and accordingly, in comparison with the conventional case, the shaft member is difficult to move to the outer side, the preliminary compression is easy to apply on the rubber-like elastic body and the distortion of the outer peripheral portion of the conventional rubber-like elastic body caused by tensile force is significantly reduced by which durability of the vibration isolating mount can significantly be promoted.
Further, by integrally molding the projected portion for the toe correcting mechanism and the restraining member by synthetic resin, the fabrication cost of the both members can be reduced, and the both members which have separately been attached conventionally by welding or press-fitting, can be attached simply at a low cost by a single step of externally fitting them onto the shaft member and by dispensing with positioning between the both members.